From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Thu, 29 Mar 2007 08:07:30 -0700 (PDT) Received: from mail.lichtvoll.de (mondschein.lichtvoll.de [194.150.191.11]) by oss.sgi.com (8.12.10/8.12.10/SuSE Linux 0.7) with ESMTP id l2TF7L6p018552 for ; Thu, 29 Mar 2007 08:07:22 -0700 Received: from localhost (dslb-084-057-114-201.pools.arcor-ip.net [84.57.114.201]) by mail.lichtvoll.de (Postfix) with ESMTP id 4542B5AD36 for ; Thu, 29 Mar 2007 17:07:19 +0200 (CEST) From: Martin Steigerwald Subject: cache flush support in SATA drives (was: Re: Questions about XFS) Date: Thu, 29 Mar 2007 17:07:18 +0200 References: <200703131440.56678.clflush@chello.be> <200703161136.32234.Martin@lichtvoll.de> <20070317004731.GA5236@jdc.local> In-Reply-To: <20070317004731.GA5236@jdc.local> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Disposition: inline Message-Id: <200703291707.18246.Martin@lichtvoll.de> Content-Transfer-Encoding: 8bit Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: linux-xfs@oss.sgi.com Am Samstag 17 März 2007 schrieb Jason White: > This might be slightly off-topic, but in choosing a SATA drive for a > desktop machine, what features/standard-complaince should one look for > in order to ensure that write barriers work? I know this involves > flushing the drive cache, but is this support mandatory in any of the > applicable standards? Hello Jason! I have no exact idea. I just now that dmesg usually tells you whether cache flushes are supported. But shouldn't modern SATA drives support NCQ anyway? Since NCQ doesn't make any sense without the ability to flush the cache, I *think* any SATA drive with NCQ support should do. NCQ support would allow the block layer to offload the write barrier request ordering at least partly to the device firmware. "ii. For devices which have queue depth greater than 1 but don't support ordered tags, block layer ensures that the requests preceding a barrier request finishes before issuing the barrier request. Also, it defers requests following the barrier until the barrier request is finished. Older SCSI controllers/drives and SATA drives fall in this category." (Documentation/block/barrier.txt of Linux Kernel 2.6.20.4) This also indicates that SATA drives should support NCQ. Regards, -- Martin 'Helios' Steigerwald - http://www.Lichtvoll.de GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7